1. Field of the Invention
The present invention relates to a pressure balancing cartridge for a mixing valve, which is used in showers and the like for mixing hot and cold water, maintaining the desired mixture even when water is used at another location on the water supply line, such as when a toilet is flushed, commonly referred to in the industry as an anti-scald mixing valve. More specifically, the cartridge of the present invention is made of a casing, an upper stem, a lower stem assembly and a balancing spool within the lower stem assembly both made of the suitable inexpensive material, creating a balancing spool which will not “seize up” or fail in bad water environments and which is protected from damage by “water hammer” shock by a shock absorbing spring, with the spring also helping to clear deposits from within the cartridge.
2. Prior Art
Heretofore, an original equipment manufacturer (OEM) model has been very expensive, because it is typically created from stainless steel, increasing product and production costs, and which does not always last very long under certain water conditions. Also, because most of the sales distribution is accomplished through specialty repackagers—i.e., people who package with their name on the product and market thousands of parts, marketing expense is also increased. Further, expenses such as catalog distribution, art work, packaging and trade shows, and sales commissions add to the final sales price. If the sale price of the repair part becomes too high, after mark up, the part often nearly costs as much as an entire new faucet.
Presently, the OEM makes the lower stem assembly of stainless steel, the purported benefits of which are intended to be durability, mainly in three areas, the seal surface areas of the O.D. of the lower stem assembly, the I.D. surface of the lower stem assembly, and the top edge of the balancing spool.
Thus, historically, spool activated pressure balancing valves have the following problems:
1. Too expensive to manufacture due to the need for machined stainless steel construction so as to eliminate spool degradation caused by peening of the end which comes into contact with a metal stem.
2. Operational defaults necessitating cartridge replacements due to the “seizing up” of the spool caused by sticking and/or jamming brought about by mineral particulate build up and aqueous debris in the water supply.
The cartridge proposed herein eliminates these problems by:
1. Integrating a shock absorbing interactive spring installed onto a top end of this spool which acts as an interface between the comparatively soft plastic spool end and a comparatively hard brass stem of the cartridge.
2. This shock absorbing feature allows the spool to be manufactured both inexpensively and with equal importance, of an ultra high temperature highly lubricitous plastic such as a PTFE compound. This type of material naturally sticks to virtually nothing, especially as compared to stainless steel.
3. This spring, during normal spool operation, performs both as a shock absorber and a mechanical device which cleans off any potential accumulated buildup by its inherent shearing action as it compresses around and over the end of the spool. Additionally this spring proactively eliminates spool seizure caused by mineral particulates and aqueous debris build up within the lower stem/spool chamber. It does so by mechanically digesting these mineral particulates and pieces of aqueous debris, reducing them down to smaller sizes that will flow freely out of the valve before they have a chance to cause a seizure default.
As will be described in greater detail hereinafter, the cartridge of the present invention overcomes these disadvantages as well as others never heretofore addressed.